Hydropneumatic motor



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C. A. BERGMANN HYDROPNEUMATIC MOTOR 4 Sheets-Sheet 1 Filed Aug. 20, 1945 ATTO/E/VEVCS,

June 27, 3950 c. A. BERGMANN 2,512,763

HYDROPNEUMATIC MOTOR Filed Aug. 20, 1945 4 Sheets-Sheet 2 June 27, 1950 c. A. BERGMANN HYDROPNEUMATIC MOTOR 4 Sheets-Sheet 3 Filed Aug. 20, 1945 BERGMANN HYDROPNEUMATIC MOTOR June 27, 1950 4 Sheets-Sheet 4 Filed Aug. 20, 1945 IN V EN TOR.

A TTORNEYSY Patented June 27, 1950 HYDROPNEUMATIC MOTOR Carl A. Bergmann, Milwaukee, Wis., asslgnor to Le Roi Company, West Allis Wis, a corporation of Wisconsin Application August 20, 1945, Serial No. 611,501

6 Claims. (Cl. 121-13) The resent invention relates in general to improvements in the art of hydraulics, and relates more specifically to improvements in the construction and operation of hydraulically actuated reci-procable piston motors of the type wherein a stroke of the piston is pneumatically cushioned.

The primary object of my invention is to provide an improved hydro-pneumatic motor which is simple and durable in construction, and'which is also highly efllcient in operation and flexible,

in its adaptations.

It has heretofore been common practice to utilize various types of portable hydraulically and pneumatically actuated reciprocating piston motors for operating diverse kinds of reciprocable and impact tools, but practically all of these prior devices have been relatively unsatisfactory and objectionable for one or more reasons. The main objection to most of these prior percussive motors is that they are sluggish in action and slow in performance of the work for which they are intended, and many of the previous devices are exceedingly dlfllcult to operate and are very tiresome to the user. Others of the prior portable .hydraulic and pneumatic impact tool actuators are complicated in structure and cumbersome to handle or manipulate, and still others are subj ect to undesirable jumping which results in rapid and excessive wear. Then too, many of these impact motors are difficult to pack or seal so as to eliminate leakage and waste of liquid, and most of the prior equipment of this kind is costly and rather limited in its uses. While some of these previous hydraulic power units have been relatively successful for the performance of certain classes of work, they were not adapted to be universally and generally applied or utilized.

It is therefore another object of the present invention to provide an improved portable reciprocable fluid actuated motor which definitely obviates all of the above mentioned difllculties and objections, and which is in fact adapted for a considerable range of uses and adaptations for which the prior devices were not well fitted.

A more specific object of my invention is to provide an improved double acting hydraulically actuated reciprocable motor assemblage which may be operated at exceedingly high percussive frequencies, thereby enabling speedy performance of the work with minimum annoyance and difficulty.

Another specific object of this invention is to provide an improved reciprocable piston hydraulic motor having relatively short piston stroke resulting in small amplitude of vibration of the portable motor and driven tool assemblage, thus facilitating operation without excessive fatigue to the user.

A further specific object of the invention is to provide an improved double acting reciprocable hydraulic motor the piston of which has greatest effective area on the return or up-stroke, and

which is pneumatically cushioned in a manner whereby excessive accumulator effect in the hydraulic system is'made unnecessary, thereby producing a portable powerful unit which is compact and light and therefore easy to handle and manipulate.

Still another specific object of the present invention is to provide a portable reciprocable piston fluid pressure actuated power unit which is extremely durable in construction, and in which annoying and dangerous vibration and jumping of the fluid pressure transmission hoses is eliminated.

An additional specific object of my invention is to provide a new and useful portable hydraulical- 1y actuated air cushioned reciprocable motor, which may be manufactured at moderate cost, all parts of which are readily accessible for inspection while being normally well protected. which may be conveniently assembled or dismantled, and which may be effectively operated with the aid of a simple constant delivery pressure supply pump.

Still another object of the invention is to provide a powerful hydraulic tool propelling unit which is well guarded against possible leakage or undesirable escape of liquid, and which may be utilized to interchangeably actuate diverse types of percussive tools.

These and other specific objects and advantages oi the invention will be apparent from the following detailed description.

A clear conception of the several features constituting the present improvement, and of the construction and operation of a hydro-pneumatic power unit embodying the invention, may be had by referring to the drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

Fig. 1 is an outside view or elevation of a typical portable hydro-pneumatic power motor and tool assemblage built in accordance with my invention, a small portion of the outer casing having been broken away to reveal internal structure;

Fig. 2 is a central longitudinal section through the assemblage of Fig. 1, taken along the line 2-2 of Fig. 3;

Fig. 3 is another central vertical section through the same assemblage, taken along a 1ongitudinal plane disposed perpendicular to the plane of the section of Fig. 2, and indicated by the line 3-3 of Fig. 1;

Fig. 4 is a transverse section through the assemblage taken along the irregular line 4-4 of Fig. 3, and showing the position of therotary automatic control valve at the beginning of the return or up-stroke of the piston;

Fig. 5 is a section similar to that of Fig. 4, but showing the position of the automatic control valve at the beginning of the impact or downstroke of the piston;

Fig. 6 is another transverse section through the motor assemblage taken along the line 66 of Fig. 3, and showing the position of therotary automatic control valve at the beginning of the return or up-stroke of the piston;

Fig. 7 is a section similar to that of Fig. 6, but showing the position of the automatic con trol valve at the beginning of the impact or downstroke of the piston;

Fig. 8 is still another transverse section through the motor unit taken along the line 8-8 of Fig. 3, and showing the position of the rotary automatic control valve at the beginning of the return or up-stroke of the piston;

Fig. 9 is a section similar to that of Fig. 8, but showing the position of the automatic control valve at the beginning of the impact or downstroke of the piston;

Fig. 10 is a longitudinal section through the piston confining casing of the unit, taken along the line Ill-l of Fig. 3;

Fig. 11 is a. circuit diagram showing a typical hydraulic power system embodying the improved portable power unit, and having the hydraulic motor for driving the automatic control valve, arranged in parallel therewith; and

Fig. 12 is a fragmentary similar diagram, having the driving motor and valve arranged in series.

While the invention has been shown and described herein as having been embodied in a system utilizing a continuously functioning hydraulic pressure supply pump and wherein the portable hydro-pneumatic motor is especially adapted to actuate an impact tool such as a paving breaker, it is not my desire or intent to thereby unnecessarily restrict the scope or limit the utility of the improved features. It is also contemplated that specific terms used herein to designate structure or movements of parts are to be given the broadest possible interpretation consistent with the prior art.

Referring specifically to the circuit diagram of Fig. 11, the hydraulic power system shown therein comprises in general a supply reservoir H for abundant liquid such as oil, and having a suitable liquid purifier or filter therein; a continuously functioning hydraulic pressure producer or pump |6 having an inlet ll communicating with the reservoir l4 at the discharge side of the filter l5, and also having an outlet H! for liquid under pressure; an adjustable safety or pressure regulating valve l9 associated with the pump outlet l8 and having an excess oil relief connection 20 for returning to the reservoir |4 liquid in excess of that required to maintain a predetermined maximum pressure in the outlet It! as determined by the setting "of the valve H); a, portable hydro-pneumatic power unit consisting primarily of a reciprocable hydraulically actuated piston 2|, a cushioning plunger 22, a detachable impact tool 23, a motor actuated automatic rotary control valve 24, a manually actuated control valve 25, and manipulating handles 26 all associated with a composite universally movable casing 21; and elongated oil supply and return conduits or flexible hoses 28, 29 respectively, connecting the pumpoutlet |'8 .with the control valve 25 and the latter with the oil supply reservoir M at the intake side of the filter |5.

The oil supp reservoir |4, oil filter l5, pressure pump l6, and pressure regulator |9 may be of any suitable and well known construction; and the portable composite casing 21 is preferably composed of a. hydraulic cylinder section 30 having a central piston confining bore 3|, a pneumatic plunger section 32 having therein a larger central bore 33 disposed in axial alinement with the cylinder bore 3|, an impact element guiding section 34 having therein a central bore 35 also disposed in axial alinement with the bores 3|, 33 and within which an impact pin 36 is'slidably confined, a tool carrying section 31 having therein a polygonal central opening 38 likewise disposed in axial alinement with the bores 3|, 33, 35 and within which the polygonal shank 39 of the tool 23 is slidable, and a handle section 40 with which the manipulating handles 26 are firmly associated, see Figs. 1, 2 and 3. The casing sections 3|], 32, 40 are firmly but detachably united by studs 4| and vibration resistant nuts 42 coacting with washers 43; and the casing sections 34, 3'! are resiliently but likewise detachably clamped against the section 32, by studs 44, vibration resistant" nuts 45 and springs 46, the latter beinginterposed between the section 31 and a reaction plate 41 which coacts with the' nuts 45, see Figs, 1 and 2. The rotary automatic control valve 24 is housed within an auxiliary casing 48 which is detachably secured to the cylinder casing section 30 by nuts and studs 49, and the manually operable control valve 25 is also housed in an auxiliary casing 50 which is also detachably secured 'to the cylinder section 3|! by the same studs 49, and to which the flexible hoses 28, 29

are attached. I I

The hydraulically actuated piston 2| which is slidably confined within the bore 3| of the casing section 30, is connected at one end to the pneumatic plunger 22 by means of a rod 5|and a universal joint 52, th latter being composed of two interfitting cylindrical elements having axes disposed perpendicular to each other and being confined within a transverse bore of the plunger 22. The :opposite end of the piston 2| is provided with another guide rod 53 which j is slidable through a sealing cap 54 detachably secured to the casing section 30 within the handle section 40, and the rod 53 is of somewhat larger diameter than the rod 5| thereby providing lesser effective pressure area at the upper or handle end of the piston 2| than at the lower or tool end thereof. The rods 5|, 53 are snugly fitted to slidein central alined bores of the casing section 30 and of the cap 54 respectively, and these bores are pro; vided with leakage oilcatching grooves 55 which are interconnected by a conduit 56 communicating through a Venturi passage 14 with the oil ber past the rods 5|, 53 will therefore be returned by suction to the hydraulic system through the grooves 55, conduit 56, and passage 14; and the for preventing possible production of excessive internal air'pressure due to reciprocation of the piston rod 53 therein.

The pneumatic plunger 22 which is slidably confined within the bore 33 of the casing section 32, and which is direct connected to the piston 21 by the rod 5| and universal joint 52, is normally movable by the piston from uppermost position :as illustrated in Fig. 2 to lowermost position as shown in'Fig. 3, and vice versa. The casing section 32 is provided at it medial portion with air inlet passages and ports 58 and air filters 60 through which air is adapted to be admitted to the up-st-roke cushioning chamber 6| of the casing section 32 when the plunger 22 is moved to its lowermost down stroke position; and the air cushion thus provided, combined with the differential pressure areas of the piston 22, cause the piston and plunger to produce a rapid impact down stroke and a slower return stroke during each of the successive reciprocations of these elements. 'Ilhe outer end of the plunger 22 is cooperable with the inner end of the impact pin ,36' which is slidable within the bore 35 of the casing section 34, and the outer end of this impact pin 36 is cooperable with the inner end of the polygonal tool shank 38 which is slidable in the opening 38 of the casing section 31, as shown in Figs. 2 and 3. While the tool shank 39 is shown as being polygonal in order to prevent rotation of th tool 23, this shank may be cylindrical; and the tool 23 is provided with a medial flange I52 which is cooper-able with a retainer spring 63 carried by the reaction plate 41, in order to prevent the tool from dropping away from the'power unit and out of the opening 38.

The improved rotary automatic control valve 24 which is housed within the auxiliary casing 48, constitutes an important featur of the present invention, and this valve 24 is cylindrical and is rotatable within a ported bearing sleeve 64 fixed within the casing 48, by means of a rotary driving motor 65, see Figs. 1, 3, 11 and 12. As shown, the rotary motor 65 is of the hydraulic type, adapted to be driven by liquid under pressure derived from the pump I6 through the pressure hose 2'8 and returned to the reservoir l4 through the return hose 29 whenever the power unit is operating; and the hydraulic motor 65 may either. be arranged in parallel with the valve 24 as in Fig. 11, or in series as in Fig. 12. The motor 65 may however be an electric or other type of fluid pressure actuated motor, operable at relatively high speed preferably at one-half the speed of percussive frequency of the hanmier, and actuating liquid may be admitted to the hydraulic motor 65 through a pipe or conduit 66 while spent liquid may be delivered therefrom through a pipe or conduit 61 as clearly illustrated in Figs. 1, 11 and 12. The rotor oi the motor 65 is direct -connected to the rotary valve 24 by means of a flexible coupling '68, and the motor 65 seals one end of the valve confining bore of the casing section 48 while a closure plate 68 seals the opposite end thereof as illustrated in Figs. 1 and 3. The speed of the motor 65 may also be-controlled with the aid of an adjustable needle valve 18 shown in Fig. 1.

The cylinder casing section 30 is provided with passages 1|, 12 which connect the lower and upper displacement chambers respectively of the piston 2|, with the lower and upper extremities of the rotary valve 24; and the casing section 38 is also provided with pressure liquid supply and spent liquid exhaust passages 13, 14 respectively of which the supply passage 13 may be cylindrical, but the exhaust passage 14 is of Venturi shape, see Figs. 2, 3, 6, 7, 8, 9 and 10. These passages 13, 14 communicate at their corresponding ends with the manually operable control valve 25, and the opposite end of the supply passage 13 communicates with the medial portion of the automatic valve 24 through a conduit 15, while the passage 14 likewise communicates with the medial portion of this valve 24 through another conduit 16. As previously indicated, the oil leakage conduit 56 which communicates with the grooves 55, connects with the constriction of the Venturi passage 14 thus providing an automatic pump for returning leakage oil to the return hose 2!! and reservoir I4. The passages 1|, 12 are also directly communicable with the pressure liquid supply passage 13 past check valves 11 and a conduit 18 as illustrated in Fig. 10 in order to prevent excessive liquid pressure from being established within the piston displacement chambers under abnormal conditions of operation, but these valves 11 will normally remain closed.

The ends of the conduits 15, 16 adjacent to the rotary automatic valve 24 are bifurcated and formed so as to perfectly balance the pressures acting upon this valve in every direction and under all conditions of operation, whereby minimum power is required to operate the valve 24 and the wear is also reduced to a minimum. The automatic valve 24 is furthermore provided with longitudinal through passages 18 in order to insure effective end balancing thereof, and has diametrically opposite ports 80 therein which are communicable with the passages II, 12 and conduits 15, 16 when the valve is rotating, in a manner whereby uniform and rapid rotation of the automatic valve by the motor 65 will be insured at all times when the unit is operating. This rotation of the automatic valve 24 causes the piston .2l and plunger 22 to rapidly reciprocate with an impact forward or down motion and a slower return or upward movement produced by the unbalanced pressure areas on the piston and the pneumatic cushioning of the plunger, and the manually manipulable control valve 25 may be utilized to effect operation of the power unit at will.

As previously indicated, the manual control valve 25 which is of the piston type, is slidably confined within the auxiliary casing 50, and this valve is adapted to either connect the hoses 28, 29 directly with each other so as to permit free circulation of liquid by the pump 16 when the power unit is not in use, or to admit liquid under pressure to the motor 65 and cylinder casing section 3|] and to exhaust spent liquid therefrom when the unit is being operated. The casing 50 is provided with a pressure liquid supply port 8| which is communicable through the valve 25 with the pressure passage 13 of the casing section 38, and is moreover provided with a spent liquid exhaust port 82 which is likewise communicable through the valve 25 with the exhaust passage 14. The valve 25 is movable with the aid of a stem 83 which is constantly urged in one direction by a helical compression spring 84 so as to move the valve toward inactive or neutral posi: tion, and the stem 83 coacts with a lever 85 which is in turn engaged by another lever 86 pivotally suspended from the casing section 40 and extending along one of the handles 26 as shown in Fig. 3. Whenever the lever 86 is pressed toward the adjacent handle 26, the spring 84 will be com pressed and the valve 25 will be moved into active position as shown, and the double lever actuating assemblage permits the valve to be thus readily actuated without undue effort.

As previously indicated, the hose connections 28, 29 are flexible and should be of suflicient length to permit the power unit to be moved universally throughout a considerable range, and the handles 25, piston 2|, and rods '53 are preferably formed hollow so as to reduce the weight of the unit to a minimum. The various casings of the assemblage should also be formed as light as possible in order to reduce the total weight of the unit to a minimum, but all elements should be sturdily constructed and are normally well lubricated when oil is used in the hydraulic system. The piston 2|, rods 5|, 53, plunger 22, impact pin 35, rotary valve 24 and reciprocable valve 25 should be carefully machined so as to accurately fit the bores with which they cooperate, and the several sections of the casing should be firmly united with the studs and nuts provided for this purpose.

During normal operation and use of the improved hydro-pneumatic power unit, the operator may readily apply a suitable tool 23 to the casing section 31 in an obvious manner, and by thereafter manipulating the lever 85 so as to shift the manual control valve 25 into the position shown in Fig. 3, liquid under pressure will immediately be admitted to the motor 55 which will cause the rotary automatic valve 24 to revolve at high speed. The rotation of the valve 24 will alternately admit liquid under pressure to the opposite sides of the hydraulic piston 2|, and will cause this piston to reciprocate within the casing bore 3| at relatively high speed. The reciprocation of the piston 2| will be imparted to the pneumatic cushioning plunger 22, which will therefore be reciprocated simultaneously with the piston 2|. During the return or up-stroke of the piston 2|, liquid under pressure will be admitted to the larger face thereof and would normally cause the piston 2| to move at high speed, but the return stroke of the piston 2| is retarded and cushioned by the compression of trapped air in the chamber 5| by the plunger 22. This compression of air naturally retards the return motion of the piston 2| and stores up energy in the compressed air confined within the chamber 6|.

As the piston 2| reaches the limit of its return stroke, liquid under pressure is admitted to the opposite face of the piston 2| whichhas considerably smaller effective area. The piston 2| will then be urged downwardly and this movement will be assisted by the compressed air confined within the chamber Bl, thereby producing a rapid impact or down stroke of the piston 2| and plunger 22. The plunger 22 will then impinge against the impact pin 35 against which the shank 39 of the tool 23 is being pressed by the operator with the aid of the handles 25, and

a powerful impact will thus be imparted to the tool 23 during each forward or down stroke of the piston 2| and plunger 22. It is to be noted that the fluid admission ports in the bearing sleeve 54 and which communicate with the'ports 80 of the valve 24 during the up-stroke as in Figs. 6 and 8, are of greater circumferential extent than the other admission ports which communicate with the ports 50 during the impact or down-stroke as in Figs. 7 and 9. thus effecting fluid admission to the piston for shorter duration on the impact stroke. In this manner, the functioning of the valve 24 is accurately 8 timed to maintain the hydraulic forces in phase with the velocity of the reciprocating piston 2| and plunger 22.

The operation of the balanced automatic rotary control valve 24 during normal use of the improved power unit, is clearly shown in Figs. 4

to 9 inclusive, wherein the position of this valve 24 at the beginning ofthe return or up-stroke of the piston 2| and plunger 22 is'depicted in Figs. 4, 6 and 8, whilethe position'of the rotary valve at the beginning of the impact or down stroke of the reciprocable elements is illustrated in Figs. 5, '7 and 9. When the rotary valve 24 is being revolved by its auxiliary motor 55 all liquid flowing through the hoses 28, 29 will normally flow through the valve'to and from one or the other displacement chambers of the pis ton 2|; but if for any reason an abnormal pressure is created in etiher of these displacement chambers, then such abnormal pressure will be automatically relieved through the check valves I1 and the conduit 18, shown in Fig. 10. I The bal anced rotating valve 24 will therefore operate smoothly at all times and will never create objectionable vibration in the unit.

The foregoing cycle of operation will be rap idly repeated so as to deliversuccessive impacts to the tool 23, and the flexible hoses28, 29 will absorb the slight pressure variations in thesupply and return lines. This relatively small am plitude of vibration of the tool is due to the comparatively short piston stroke utilized, and results in operation of the unit with extremely high percussive frequencies, thereby permitting the work to be rapidly accomplished. The use of a double acting hydraulically actuated piston, with a smaller eifective area for the down-stroke, in combination with a cushion for the up-stroke which produces a piston velocity characteristic approaching a sine curve, reduces the capacity of the accumulator required for constant flow in the oil supply and return line to such an extent that the accumulator effect of the flexible hose is amply sufiicient to prevent excessive pressure variations in the oil lines. Undesirable jumping of the hose is thus eliminatedwithout using an additional accumulator and the wear and tear of the hose is thus reduced to'a minimum. Leakeage or undesirable escape of oil from the system, is also positively prevented by utilizing the Venturi pumping effect of the passage 14 to return oil leakage to the supply reservoir. The manually actuated control valve 25 with its liq- -uid return port, obviously permits the use of a constantly operating supply pump l6, since the oil is by-passed through this valve when the power unit is not in use, and the safcty relief valve l9 will positively prevent the pump Hi from being subjected to undesirably high pressures at improved portable device while being relatively light in construction and therefore readily manipulable, is devoid of undesirable vibrations and is therefore operable for long periods of time.

without excessive fatigue to the operator. By

eliminating, necessity of utilizing an accumulator, the size or bulk of the unit is reduced to a minimum, but in spite. of its size the improved hydraulic motor is exceedingly powerful and re- 'anced so as to insure smooth operation, and

wear is reduced to'a minimum; and as previously indicated, the auxiliary hydraulic motor 65 may be replaced by any suitable type of motor adapted to rotate the valve 24 at the desired speed. While a rotary valve is preferable because of its smooth operation and ease of balancing, a reciprocable or other type of automatic valve may be utilized; and the automatic valve whether rotary or otherwise, may assume various shapes. The accurate timing of the control valve 14 is also important in order to maintain the proper phase relation between the functioning-f the resilient cushion 6| and the piston 2! so as to insure delivery of effective impact blows while causing a continuous stream of the actuating liquid to flow through the power unit; and the totally balanced valve 24 coacting with properly proportioned inlet ports makes it possible to effect such accurate timing and to produce .smooth operation with minimum vibration. Any

desired type of elastic medium may also be substituted for the pneumatic cushion shown, without departing from this invention, and the power unit may also be produced in various sizes. The improved unit may obviously be utilized to drive diverse types of impact tools, and all parts of the implement are relatively simple in construction and are. also conveniently accessible for inspection.

It should be understood that it is not desired to limit this invention to the exact details of construction or to the precise mode of use, herein shown and described, for various modifications within the scope of the appended claims may occur to persons skilled in the art.

I claim:

1. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having diiferential oppqsed faces alternately exposable to incompressible fluid under pressure, a totally balanced valve associated with said casing in proximity to said bore and being movable to alternately admit said .fluid to said opposed piston faces, and resilient means for storing energy delivered by said piston when travelling in one direction and for returning said energy to the piston when moving in the opposite direction to cause said piston to deliver impact blows when travelling in said opposite direction, the movement of said valve and the operation of said energy storing means being timed so that said fluid will be admitted tothe smaller face of said piston and released from the opposite face precisely when said means reaches its maximum energy storing position.

2. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having differential opposed faces alternately exposable to incompressible fluid under pressure, a totally balanced valve associated with said casing in proximity to said bore and being constantly rotatable to alternately admit said fluid to said opposed piston faces, a motor operable by said fluid to constantly rotate said valve in the same direction, and resilient mean for storing energy delivered by said piston when travelling in one direction and for returning said energy to the piston when moving in the opposite direction to storing means being timed so that the valve will admit fluid to the smaller piston face and will simultaneously release fluid from the opposite piston face precisely when said means reaches its maximum energy storing position.

3. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having differential opposed pressure areas alternately exposable to incompressible fluid under pressure, a totally balanced valve associated with said casing in proximity to said bore and being constantly movable to alternately admit said fluid to said opposed piston areas, and a pneumatic cushion for storing energy delivered by said piston when travelling in one direction and for returning said energy to the piston to produce impact blows when moving in the opposite direction, the movement of said valve and the operation of said energy storing cushion beingtimed so that said fluid will be admitted to the smaller of said piston areas and will be simultaneously released from the larger piston area precisely when said cushion is subjected to maximum energy storing compression.

4. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having differential opposed pressure faces alternately exposable to incompressible fluid under pressure, a totally balanced valve associated with said casing in proximity to said bore and being constantly rotatable to alternately admit said fluid to said opposed piston faces, a motor operable by said fluid to constantly rotate said valve in the same direction, resilient means for storing energy delivered by said piston when travelling in one direction and for returning said energy to the piston to produce impact blows when moving in the opposite direction, the rotation of said valve and the operation of said energy storing means being timed so that the valve will admit said fluid to the one of said piston faces and will release fluid from the other face when said means reaches its maximum energy storing position, and means for circulating a continuous stream of said fluid in parallel from a source of supply through said motor and said valve and past said piston faces.

5. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a piston reciprocable within said bore and having opposed faces alternately exposable to liquid under pressure, a totally balanced valve associated with said casing in proximity to said bore and being constantly rotatable to alternately admit said liquid to said opposed piston faces, and resilient means for storing energy delivered by said piston when travelling in one direction and for returning said energy to the piston when moving in the opposite direction, the rotation of said valve and the operation of said resilient means being timed to cause the valve to admit said fluid to the piston face farthest from the energy storing means and to simultaneously release fluid from the opposite piston face precisely when said means has reached its maximum energy storing position.

6. In a hydraulically actuated reciprocable impact motor, a casing having a bore, a, piston reciprocable within said bore and having differential opposed pressure faces alternately exposable 11 to incompressible fluid under pressure, a totally balanced valve associated with said casing in proximity to said bore and being constantly rotatable to alternately admit said fluid to said opposed piston faces, a motor operable by said 5 fluid to constantly rotate said valve in the same direction, resilient means for storing energy delivered by said piston when travelling in one direction and for returning said energy to the piston to produce impact blows when moving in the opposite direction, the rotation of said valve and the operation of said energy storing means being timed so that the valve will admit said fluid to the one of said piston faces and will release fluid from the other face when said means reaches its maximum energy storing position, and means for circulating a continuous stream of said fluid in series from a source of supply through said motor and said valve and past said piston faces.

CARL A. BERGMANN.

12 n-nrnnsnoss man UNITED STATES r a'rnn'rs Number Name 1 Date Re. 9,408 Harrison Oct. 12, 1880 159,242 Winchester Jan, 26, 1875 412,517 MacCoy Oct.- 8, 1889 538,840 Morgan May 7, 1895 581,572 Cartlidge Apr.'27, 1897 1,306,067 Krause June 10, 1919 1,921,753 Hofiman Aug. 8, 1933 2,047,832 Morton 'July 14,1936 2,241,645 Peterson May 13, 1941 2,290,558 Helms July 21, 1942 2,311,443 Keeler Feb. 16, 1943 2,329,709 Fischer Sept. 21, 1943 

